Mining salt.



H. FRASGH.

MINING SALT.

APPLICATION FILED FEB. 16, 1899.

HIM 'fi F PATENTED DEC. 24, 1907.

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Witnesses ja/eiz to;

yam 0% UNITED STATES PATENT OFFIGE. HERMAN FRA'scH, or CLE-VELAND, oH'Io, ASSIGNOR T THEUNITED SALT COMPANY, OF CLEVELAND, OHIO, A CORPORATION OF OHIO.

MINING SALT} Specification of Letters Patent.

Patented Dec. 24, 1907.

I Application filedPebruary 161 1899. Serial No. 705,604-

I and exact description of the invention.

This invention relates more especially to the recovery of common salt or like sub.-

' stance from a natural (subterranean or other) deposit, by means of a salt solution which is formed in the deposit or salt bedand is removed to the surface of the ground and from which the saltis then-recovered: but each of the improvements forming part of said invention is intended to be-secu'red forall the uses to which it may be adapted. Some'of the said improvements extend to the recovery of salt or like substance. from artificial deposits or masses.

Heretofore in salt-mining by water, it has been customary to introduce substantially pure water at ordinary atmospheric. tempera-- tures into the underground de osit, to allow the water to become saturate with the salt in said deposit, to remove the so-formed brine to the surface of the ground, and to evaporate it in suitable evaporators by means of close steam ipes immers'edin the brine.

Of course the rine from the underground deposit can be evaporated in evaporators of other known forms; but so far as I am aware, it has generally been found most advantageous heretofore to use evaporators in which the evaporation hasbeen produced by heat imparted to the brine by means of close steam pipes. v

In the case of deposits containing gypsu (hydrated calcium sulfate) along with the common salt, the brine obtained is charged with calcium sulfate; and this substance precipitates, when the brine is heated and evaporated, and thereby forms on the steam pipes (or on any other heat-transmitting walls which might be used) an incrustat'ion which diminishes the transmission of .heat through the conducting Walls and makes necessary a material increase of the heating surface over what would suffice were it not forsuch. incrustatl'on, a The incrustation also necessitates troublesome and expensive cleaning. in which brine is evaporated from salt have to be cleaned twice a day by boiling the pans In my experience, vacuum pans.

out with fresh water and-scraping their flues.

This cleaning reduces .the working'time and also the output of the pans, besides being expensive in itself. Open pans have their heating pipes cleaned once a week; and even with a large force of workmen much time is lost;

-While, besides, owing-to the hardness and strong adhesion of the incrusting coat, it is necessary to knock it OE With hammers,

whose repeated blows shorten the life of the pipes, notwithstanding the fact that they are made extra heavy for the purpose of with standing. the hammering as long as possible.

The pipes are apt to split after a certain time, when of course they will no longer retain the steam. To avoid such incrustation in mining salt from gypsum-containing salt beds is one, and a veryimpor'tantone, of the objects of the present invention; but this latter has ad- A vantages, irrespective of the presence of gypsum in the salt bed, and is so claimed as well as in its application to gypsum-containing salt beds or other like deposits. tage is that more'salt canvbe obtained for a given amount of coal than by the old procedure as described above.

In accordance with the present invention unsaturated brine is introduced into the natural salt de osit, and allowed to dissolve the salt thereo (preferably to saturation of the brine) and. the brine thus charged with more or less of the salt from said deposit, as well as with that 'originally'in the brine, is removed from'the deposit and made to give up salt by cooling and artial evaporation, the residual brine being leated and diluted for reuse'in a succeeding round of operations.

. This improvement can be carried out 1n out, it has the advantage over the procedure described above as heretofore m use, that the artial evaporation and cooling, and the One advana various Ways; and however it may be carried revented altogether); but even-if it walls or to adjust the temperatures otherwise than with a viewto lessenlng theprecipitation of calcium sulfate along with the salt, nevertheless the new procedure indicated above would still be advantageous. For exannle, a descending column of unsaturated brine on its way to the salt de )osit more nearly balances the column of rine ascemling therefrom on its way to the evaporating apparatus than does the column of water, which is introduced into the salt posit an d. heating the resultant brine in order to evaporate the same. 7

The operations of the new procedure can be carried on at any desired temperatures, so long as there is a suitable difference of temperature between the unsaturated brine supplied to the salt deposit on the one hand and the residual brine'before it is diluted and heated for reuse on the other; but in dealing with gypsum containing deposits there are special advantages in carrying on the operations with reference to the varying solubility of calcium sulfate in water at different temperatures.

ater somewhere between 32 C. and 41 C. (which correspond, respectively, with 89,, and 105 i degrees of Fahrenheitsthermometer) has its maximum capacity to dissolve calcium sulfate, so that its capacity be comes less, whether the temperature of the water is raised above 41 C. or is lowered below 32 C. if residual brine remaining after the recovery of salt from the brine from a g psum containing deposit and having a temperature of not less than 32 C. is heated to above 41 (l. preparatory to its introduction into said deposit, or if residual brine of less than 32 C. is heated so far above 41 C. that the difference between its temperature and 32 0. would be less than the difference between 41 C. and the temperature of the brine supplied to the salt deposit, the effect of this adjustment of temperatures in either case is that the brine entering the salt deposit is more nearly saturated with calcium sulfate than it is with common salt; for the heating of the residual brine for reuse to above the temperature of maximum solubility of calcium sulfate increases the capacity of the water of said brine to hold salt in solution, while it reduces thccapacity thereof to hold calcium sulfate in solution. Moreover, when the brine, after removal from the salt deposit at a temperature above that of the maximum solubility of calcium sulfate, is cooled in order to recover salt therefrom, the cooling increases the capacity of the water to hold the calcium sulfate in solution, while it diminishes the capacity of the water to hold salt in solution. Hence it is possible to precipitate pure salt from brine charged with calcium sulfate. The higher the temperature of the brine in the salt bed above that, of the maximum solubility of calcium sulfate, the less the percentage by weight of calcium sulfate necessary to saturation; so that the aqueous liquid at such higher temperature, even if it were pure water, would dissolve less calcium sulfate than it would if not so highly heated.

Apart from any consideration of calcium sulfate, it is advantageous to have the brine in the salt deposit at as high a temperature as can economically be secured; for the higher such temperature may be above atmospheric temperature, the more readily can the brine on removal be lowered a given number of degrees.

The cooling and the partial evaporation of the brine from the salt deposit can be performed separatclyfrom each other, if preferred; and, whether performed separately or together, they may be effected in any suitable way; but a special improvement consists in effecting the partial. evaporation (or at least a substantial part thereof) at the expense of heat in the brine when it leaves the salt deposit, and thereby eil'ectinga lowering of the brines temperature (as well as a par tial evaporation) in one and the same opera.- tion. thereby be dispensed with; although all use of such Walls is not necessarily excluded.

In order to avail oneself of a larger proportion of the heat in the brine when it leaves the salt deposit than would take place by simple evaporation in the air, the aqueous vapor can be removed by exhaustion from the evaporating brine.

The heating and dilution of the residual brine can be performed separately from each other; and, whether performed separately or together, they may be ell'ected in any suitable way; but aspecial improvemeiit consists in effecting the'heating (or at least a substantial part thereof) by condensation of steam in contact with the residual brine and there'- by eil'ecting also a dilution of the brine in the one operation. The condcnsatimi may take place at atmospheric or at other than atmospheric pressure; and the ratio of heating to dilution can be varied by changes in pressure. Addition of water may also be resorted to if more dilution should be desired.

As thus far described it is essential to the The use'of heat conducting walls caninvention that unsaturated brine should be introduced into a natural salt deposit, should dissolve salt in said deposit, should be re- 2 6 I in r moved therefrom, should be cooled and partially evaporated (separately or together) for recovery of salt, and should beheated and diluted (separately or together) for reuse, the round of ,operations being continued as desired. It is possible, however, without encroaching on the prior state of the art, to omit one or more of these features; and it is intended to. include all new, original and useful features of the invention as broadly as the prior state of the art will permit. Omissions, additions and other modifications may be made indefinitely so long. as the substance is taken of any one or more of the claims at the end of this-specification.

The main and perhaps exclusive use of the present invention will, it is believed, be

found in the recovery of common salt; and the several. improvements are, therefore, described and clalmed herein in terms as applied to such recovery, it being left to the reader to make necessary changes to adapt the description and claims to other a propriate water soluble substances to whic it may be'desired to apply the invention, or any part thereof. If the substance to be recov-' ered should be contaminated with impurities whose solubility should vary-with r1se-of temperature inversely as does the substance to be recovered, what is herein described with reference to common salt and gypsum may be applied; and if, in an case, the substance to be recovered shoul be less soluble at higher than at lower'temperatures,- the heating and cooling may be reversed, thatis to say, according to one mode, the substance.

can be recovered by heating and partially evaporating the solution obtained from the deposit of such substance,- the residual mother liquor being prepared .forreuse by cooling anddilution.

1 In the accompanying drawing: Figure 1 is a view partly in elevation and partly in section of a salt mining plant suitable for carrying the invention into effect; Fig. 2 is a sectionalelevation of an evaporator which .may be substituted fo; the vacuum pan of Fig. 1'; and Fi is an end view of still another form o evaporator, themiddle portion being brokenaway. 1

'The salt well" shown is of ordinary construction, the casing A is driven to the top of the solid limestone rock B, through which" the uncased bore extends tethe' natural salt deposit C; and there is a pump D forcing the aqueous liquid down the casing A into-the salt deposit 0 and removing-the same. charged with salt from said. deposit up through the tubing E, which passes through a stuffing box 2 in the casing head-A This also is a common arrangement.

In accprdanee with the main portion oflthe present invention unsaturated brine isused as the aqueous solvent liquid, This unsaturated brmeis forced into the deposit 0 by the .pump' D, and after becoming charged with salt from said deposit C it is forced up the'tubing E and is delivered by the pum F through the pipe 8 into the vacuum pan or the evaporator G (Fig. 2) or G (Fig. 3) or other suitable apparatus for cooling and partially evaporating the (ordinarily saturated) brine. In'this apparatus the brine is forced to give up a portion of its salt, in consequence of the reductionin temperature and the loss of water; and the residual brine passing through the pi e 4 to the pump H is (by the latter) forced through the pipe 5.into the steam-condenser J or other'ap aratus for heating and diluting thesaid residual brine, $0

from which the pump D takes the now no longer saturated brine, having its tempera ture restored, and forces it into the salt depositC onanew round. The temperature which the unsaturated 8f; brine has on entering the salt de osit C will depend upon how much heat. s all be allowed to accumulate therein. For example assuming that the heat and moisture abstracted in the vacuum pan G, or one of the other evaporators (G and G respectively) or other cooling and evaporating apparatus shall equal the heatand moisture added to the residual brinefin the vessel J, or other heating and .diluting apparatus, and that there areno otherlosses, it is evident-that whatever temperature. shall be given the unsaturated brine at the startwill be maintained. Practically it is convenient to obtain all the evaporation'of thecharged brine which may be consistent with a full delivery of saturated .brine bythe pump F, and to adjust the temperature by regulating the volume and temperature of the steam admitted into the vessel J, the pressure in said vessel J being allowed to accumulate if the temperature is to be carried above the boiling point at atmospheric pressure of the unsaturated brine'. If other form of heater be used, the temperature can be appropriately regulated. It is also desirable to have the solvent liquid in the deposit C above atmospheric. temperature, and if the said deposit contains gypsum (as is generally the case) to have it above the temperature of maximum solubility in Water of calcium sulfate, which as alreadyexplained is somewhere between 32 C. and 41 (3.; temperatures much higher than the highest of these limits are I recommended for the unsaturated brine. I

Evaporators in which evaporation is carried on without loss of temperature are well known but such evaporators in'- their best forms have heat conducting walls for trans-' mitting tojthe brine the heat which becomes *latentin the water vapor produced by the As hereinbefore explained, there are disadvantages in the use of such surfaces; especially when the evaporating brine contains calcium sulfate; and conse-;

evaporation.

quently use is made more advantageously of evaporators in which the evaporation takes place at the expense of heatin the brine, whose temperature is thereby lowered through the absor 'tion of heat energy (in the form of latent cat) by the Water vapor produced.

In Fig. 1 the cooler and evaporator G has a long outlet pipe 6 whose lower end is sealedby immersion in the residual brine in the salt collector G*, the length of said pipe being proportionate to the vacuum to be maintained in said vessel G. A sprinkler or rose 7 is shown on the end of the pi e 3 for delivering the brine into the vesse G. At its upper end a'connection leads to the vapor cond enser K, into which cold water from the pipe 8 is showered through the rose 9. This shower condenses most of the water vapor from the vessel G; and any uncondensed vapor is taken oii by the ipe 10, which leads to a vacuum ump. he vapor as it forms in the vessel is thus continually exhausted, and the rapidity of evaporation from the brine in said vessel is correspondingly increased.

The vapor condenser is provided with a long'outlet pipe 11 to sup ort a columnof water correspondin with t e vacuum. The salt is taken out oi the collector G* in any suitable way, a bucket conveyer L being shown for the purpose and a salt wagon M being also shown 1n osition to receive the salt as it is delivered y the conveyer L. In Fig; 2 the vessel G is open to the air and should be of such dimensions to expose a large area of brine. The rose 7 is turned up, so as to expose the brine in jets to the atmosphere. A screw conveyer Lf is shown for taking oif the salt which precipitates in consequence of the cooling and evaporation which take place in said vessel G.\

In Fig. 3 there are shown long shallow ans G, open to the air and placed on a ame N. They are connected in series so that the brine from the salt bed C enters one of the top pans (the left hand pan as shown) flows its full length, returns through another pan of the top row, until it reaches the last of this row (the right hand top pan as shown) then it flows through the pipe 12 into the first pan of the next row, and passes successively through the ans of this row: the pipe 13 delivers it into t e first pan of the bottom row; and after it has passed in succession through the pans ofthis row, it escapes as residual brine by the pipe 4, which conducts it to the pump H to be delivered (cooled and partly evaporated as compared with its state after removal from the salt-bed G) into the vessel J, or other heating and diluting ap aratus.

n the avaporators of Figs. 2 and 3, the evaporation takes place at the expense of heat stored in the brine, but the benefits of an exhaustion of the vapors (as in the evaporation of Fig. 1) is not obtained. They should be placed in a well ventilated building, so that the air above the brine shall not become'saturated.

Heaters in which the elevation of temperature is efiected without gain (or even with a loss) of volume of liquid heated are well =known; and the apparatus for heating and dilutin'gthe residual brine may consist of one or more such heaters, in connection with means of any suitable description for introdueing the diluting liquid into the residualbrine before or after, or partly before and partly after, it enters the said heater or heaters, or while it is therein; but in such heaters use is made of conducting walls to transmit the heat to the brine; and as explained in the earl part of'this specification there are objectlons-to or disadvantages in the use of such walls. Heaters in which water is raised in temperature by condensation of. steam therein are also known; and any such heater may be used with or without additional means of diluting or heating or both.

Exhaust or live steam or both may be used; but exhaust steam has the advantage of economy; and in the case of brine-heating there is the special advantage that the avidity '4 of the brine for moisture can condense steam after it has reached-the temperature of the exhaust steam, with the result of raising the brine more nearly to its own boiling point above the temperature of the steam. So far as I am aware this principle was never before utilized in mining salt or in fact in any recovery of salt. I As shown the vessel J is provided with rings 14 and central disks 15 for bringing the steam and the brine more intimately in contact with each other; and with the same object there is a sprinkler or rose 16 on the end of the pipe 5 which delivers the residual brine into the vessel J. The pipe 17 delivers the steam into, the, bottom of the vessel J. This may be exhaust steam from the engine P, which is exhausted through the' pipe 21; or live steam from the pipe 20 (which supplies said engine P) may be admitted through the valve 19, which is closed when live steam is not desired. The vessel J could be connected directly with a steam enerator irrespective of any engine. If l mowever, the plant is run on exhaust steam, it may sometimes be desirable to admit live steam along with the exhaust steam, or to run temporarily on live steam in case the sources of exhaust steam should be cut oil.

At 18 a safety valve is shown for preventing the accumulation of back pressure on the engine P, should brine accumulate in the vessel J. At 22 is a pipe for carrying off any surplus steam.

With the vessel J open to the atmosphere (through the pipe 22 for example) it is not being dispensed with. More work would be; placed on the pump H, as it would have to force the residual brine against the pressure in the vessel J.

Even if the vessel J be open to the atmos phere, the pump D, or its equivalent, could be dispensed with if the difference in weight per square inch of cross section of the col umns which respectively descend in the easin A and bore in rock B and ascend in the tu ing E were less than the atmospheric pressure.

Where there is suflicient pressure in the casing head A, the pump F can be dispensed with. The residual brine could be delivered into thevessel J (or other heater) by gravity, if the evaporator were at a suflicient elevation, or ifan elevated tank were used.

In working under superatmosplieric pressure, the temperature of the brine may be such that it has to be held under superatmospheric pressure, in order to prevent it from generating steam in the tubing E and pipe 3 and thereby precipitating salt in them: in such case provision is'madein any known or suitable way for holding the hot brine under pressure until it isdischarged into the evaporator. On its'esca'pe, partial evaporation and cooling would take place immediately, and might be continued inthe same or in other apparatus, with or without an exhaustion of the vapor.

In working under atmospheric pressure in the heater J with exhaust steam, the residual brine and the water of condensation can be raised to between 212 F. andv 220 F.; andthe temperature of the residual brinein the' evaporators G G or G can be reduced to about 80 F.; and the working with exhaust steam at substantially these temperatures is recommended.

In my application No. 736,842, filed November' 13, 1899, I have described and claimed 7 improvements, which (as so described) embody features that'are also described herein or that may to some extent be suggested by What is herein described. These features, however, concern only the separation of common salt or like substance from solution; while the claims herein are all of them limited. to processes which include as essential cooperating parts both the formation of a soluti on as specified in the respective claims and the separation of the common salt or like substance from the so formed solution. The improvements claimed in my are designed (when so desired)-to be used otherwise than in carrying out the processes claimed herein; which latter constitute, in fact, a distinct subject of invention.

I claim as my invention or discovery 2- 1. The improvement in mining salt, consisting in introducing unsaturated brine into a natural deposit of salt, removing it charged with salt from said deposit, recovering salt by cooling and partially evaporating the charged brine, preparing the residual brine for reuse by heating and dilution, and so contiriuing, substantially as described.

2. The improvement in mining salt, consisting in introducing into a natural gy sum containing deposit of salt unsaturated rine heated above the temperature of maximum solubility of calcium sulfate, removing it charged with'salt from's'aid deposit, recovering salt by cooling and partially evaporating the charged brine in such manner as to leave a residual brine whose temperature is nearer to that of said maximum solubility than is the temperature of the brine supplied to the deposit, reparing the residual brine for reuse by d1 uting and heating, and so continuing, substantially as described.

3. The improvement inmining salt, con sisting in introducing into a natural deposit of salt unsaturated brine heated above the atmospheric temperature, removing it charged with salt from said de osit, recovering salt by cooling and partial y evaporating the charged brine, preparing the residual brine for reuse by heating and dilution, and so continuing, substantially as described.

4. The improvement in mining salt, consisting in introducing unsaturated brine into a natural deposit of salt, removing it charged with saltfrom said deposit, recovering, salt by evaporation at the expense of heat in said brine when it leaves the deposit, so as to well as a partial evaporation, preparing the residual brine for reuse by heating and dilution, and so continuing,"substantially as described.

5 The improvement in mining salt, consisting in introducing into a natural gypsum containing .deposit of salt unsaturated brine heated above the temperature of maximum solubility of calcium sulfate, removing it charged with salt from said deposit, recoverefiect thereby a lowering of temperature as mg salt by evaporation at the expense of heat in said brine when it leaves the deposit, so as .to effect thereby a lowering of temperature as well as a partial evaporation and the lowering of tem erature being such as to leave a residual rine whose temperature is nearer to that of said maximum solubility than is the temperature of the brine supplied to said deposit, preparing the residual )rme for reuse by heating and dilution, and so continuing, substantially as described. 6. The improvement in mining salt, consisting in introducing into a natural deposit of salt unsaturated brine heated above the atmospheric temperature, removing 1t charged with salt from said deposit while it is still above atmospheric temperature, re= covering salt by evaporation at the expense of heat in the brine when it leaves said deposit, so as thereby to effect a lowering of temperature as well as a partial evaporation, preparing the residual brine for reuse vby heating and dilution, and so continuing, substantially as described.

7. The improvement in mining salt, consisting in introducing unsaturated brine into a natural deposit of salt, removing it charged with salt from said deposit, recovering salt by evaporation with the aid of an exhaustion of the vapors given off and at the expense of heat in said brine when it leaves the deposit, so as to effect thereby a lowering of temperature as well as a partial evaporation, preparing the residual brine for reuse by heating and dilution, and so continuing, substantially as described.

8. The improvement in mining salt, consisting in introducing unsaturated brine into a natural deposit of salt, removing it charged with salt from said deposit, recovering salt by cooling and partially evaporating the charged brine, condensing steam in contact with the residual brine to heat and dilute the same for reuse, and so continuing, substantially as described.

9. The improvement in mining salt, consisting in introducing into a natural gy sum containing deposit of salt unsaturated rine heated above the temperature of maximum solubility of calcium sulfate, removing it charged with salt from said deposit, recovering salt by cooling and artially evaporating the charged brine in sue manner as to leave a residual brine whose temperature is nearer to that of said maximum solubility than is the temperature of the brine supplied to said deposit, condensing steam in contact with the residual brine to heat and dilute the same for reuse, and so continuing, substantially as described.

1 The improvement in mining salt, consisting in introducing into a natural depos- 1t of salt unsaturated brine heated above the atmospheric temperature, removing it charged with salt from said deposit while it is stillabove atmospheric temperature, recovering salt by cooling and partially evaporating the charged brine, condensing steam in contact with the residual brine for reuse, and so continuing, substantially as described.

11. The improvement in mining salt, con-- sisting in introducing unsaturated brine into a natural deposit of salt, removing it charged with salt from said deposit, recovering salt by evaporation at the ex ense of heat in said brine when it leaves t e deposit, so as thereby to effect a lowering of temperature as well as a partial evaporation, condensing steam in contact with the residual brine to heat and dilute the same for reuse, and so continuing, substantially as described.

12. The improvement in mining salt, consisting in introducing unsaturated brine into a natural deposit of salt, removing it charged with salt from said deposit, recovering salt by evaporation with the aid of an exhaustion of the vapors given off and at theexpense of heat in said brine when it leaves the deposit, so as thereby to effect a lowering of temperature as well as a partial evaporation, condensing steam in contact with the residual brine to heat and dilute'the same for reuse, and so continuing, substantially as described.

13. The improvement in mining salt, consisting in introducing into a natural deposit of salt unsaturated brine heated above the natural temperature of the deposit, removing it charged with salt from said deposit While still above the latters natural temperature, recovering salt therefrom by cooling, preparing the residual brine for reuse by heating, and so continuing, substantially as described.

14. The improvement in mining salt, con sisting in introducing into a natural deposit of salt unsaturated brine heated above the natural temperature of the deposit, removing it charged with salt from said deposit while still above the latters natural temperature, recovering salt therefrom by )artial evaporation, preparing the residual brme for reuse by dilution, and so continuing, substantially as described.

15. The improvement in mining salt, consisting in introducing an aqueous solvent atmospheric temperature, and recovering salt therefrom by cooling and evaporation, substantially as described.

17. The improvement in mining salt, consisting in introducing into a natural gypsum containing deposit of salt, an aqueous so vent heated above the temperature of its maxi-' mum capacity to dissolve calcium sulfate, removing it charged with salt from said deposit, and recovering salt therefrom, substantiallyas described. I

18. The improvement in mining salt, consisting in introducing into a natural gypsum erases sisting in introducing unsaturated brine into a natural deposit of salt, removing it charged with salt from said deposit, and recovering salt therefrom by evaporation, substantially as described.

20. The improvement in mining salt, consisting in condensing steam in contact with an aqueous liquid andso heating it above atmospheric temperature, introducing the so heated liquid into a natural deposit of salt,

removing it charged with salt from said deposit while it is still above atmospheric temperature,.and recovering salt therefrom by evaporation, substantially as described.

21. The improvement in mining salt, consisting in introducing an artificially heated aqueous solvent into a natural deposit of salt, removing it charged with salt from said deposit while retainingheat imparted artificially as aforesaid, and recovering salt by evaporation, substantially as described.

22. The improvement in mining salt, consisting in introducing an artificially heated aqlueous solvent into a natural deposit of sa t, removing it charged with salt from said deposit while retaining heat imparted artificially as aforesaid, and recoverln salt by evaporation at the expense of heat in the so charged solvent when it leaves the deposit, substantially as described.

23. The improvement in mining salt, consisting in introducing into a natural deposit of salt an aqueous solvent heated above atmospheric temperature, removing it charged with salt from said deposit While it is still above atmospheric temperature, andrecovering salt by evaporation at the expense of heat in the so charged solvent when it leaves. the deposit, substantially as described.

24. The improvement in mining salt, consisting in introducing unsaturated brine into a natural deposit of salt, removing it charged with salt from said deposit, .and recovering salt by an evaporation at the expense of heat in the so charged brine when it leaves the deposit, substantially as described.

25. The improvement in minin salt, consisting in introducing into a natura deposit of salt unsaturated brine heated above the atmospheric temperature, removing it charged thereby continuing, substantially as described.

26. The improvement in recovering salt, consisting in mtroducing unsaturated brine into a mass of salt, removing it charged with salt from said mass, recovering a part of the salt therefrom, preparing the residual brine for reuse by condensation of steam in contact therewith, and so continuing, substantially as described. 1

27. The improvement in recovering salt,

consisting in condensing steam in contact with an aqueous solvent, introducing the so heated solvent into a mass of salt, removing it charged with salt, and recoveiing salt therefrom by evaporation at the expense of heat in the so charged solvent when it leaves said mass of salt, substantially as described.

28. The improvement in mining salt, consisting in introducing'into a 'natural deposit of salt thehot water from condensing steam, removing the resultant brine, and effecting the evaporation of the latter by the aid of heat] derived from such condensing steam,

substantially as described.

29. 'The improvement in mining salt, consisting in introducing into a natural gypsum containing deposit of salt unsaturated brine heated above the temperature of maximum solubility of calcium sulfate, removing it charged with salt from said do osit, recovering. salt by cooling and partia y evaporating the charged brine, preparing the residual brine for reuse by diluting and heating it,

and so continuing, substantially as described.

30. The improvement in mining salt, consisting in im arting both the latent heat of steam and t e sensible heat of its water of condensation to brine from which salt is subsequently recovered by evaporation, the water of condensation'being sent into a natural deposit of salt and so charged with salt to form brine for such evaporation, substantially as described.

31. The im rovement in mining salt, consisting incon ensing steam by imparting its latent heat to brine, mingling its water of condensationwith the so heated brine, introducing the resulting unsaturated brine into a natural deposit of salt, removing it charged with salt, and recovering salt therefrom, substantially as described.

32. The improvement in mining salt, consisting in condensing steam in contact with brine in such relative proportions as to'furnish heat sufficient to raise the temperature of the brine above that ofsaid steam, introducing the so heated unsaturated brine into a natural deposit of salt, removing it charged a with salt, and recovering salt therefrom, substantially as described.

In testimony whereof in presence of two witnesses. HERMAN- FRASCH.

- Witnesses: I

T. W. LOTHMAN :1. E. DEQKAND I afiix my signature 

